The present invention relates generally to the art of electric motors and other electromechanical machines. More particularly, the invention relates to improved methods of manufacturing housing frames for such electromechanical machines.
In the past, housing frames for electric motors and the like have been made by a variety of manufacturing processes. For example, housing frames have often been cast utilizing a reusable pattern form. In this case, the pattern form, which may be made of wood or metal, is placed in oil-impregnated sand or other suitable casting medium. After the sand is suitably packed, the pattern form is removed to leave a void of the desired shape. Next, molten metal is poured into the void, which cools to form the housing frame.
More recently, some manufacturers have begun using a "lost foam" casting technique. In this process, a pattern form of the frame to be cast is placed in a dry sand casting medium. The sand is vibrated to ensure that the pattern form is completely surrounded, without leaving undesirable voids. With the pattern form in place, molten metal is poured into the casting medium. The pattern form, typically made of polystyrene or the like, vaporizes upon contact with the molten metal. As a result, the molten metal fills the void left by the pattern form, and assumes the desired shape. After the molten metal has cooled to rigidity, the housing frame is removed from the casting medium.
The traditional manner in which "lost foam" casting has been performed is not without disadvantages. For example, it believed that others have provided different pattern forms for different frame styles to be produced, even within a single inner diameter size. In this case, it may be necessary to provide many different pattern forms. For example, a single inner diameter size may include footed and footless frames, as well as frames of different axial lengths. It would be advantageous to provide a technique with greater flexibility, in which a single pattern form can be used with multiple frame styles.